1. Field of the Invention
The present invention relates to a method of producing a laminated ceramic electronic component defining, for example, an inductor, an LC component or a feedthrough device. More particularly, the present invention relates to a method of producing a laminated ceramic electronic component which provides internal electrodes having increased thicknesses.
2. Description of the Related Art
Conventionally, a laminated inductor having a sintered body obtained by integrally firing a metal and ceramic is known. In producing such a laminated inductor, internal electrode paste to define a coil conductor is first printed on a ceramic green sheet. Also, through holes are formed in the ceramic green sheet to electrically connect upper and lower internal electrodes. A plurality of green sheets are stacked to define a laminate body, and the resulting laminate body is pressed in the thickness direction. Then, the laminated structure is fired to obtain a ceramic sintered body, and a pair of external electrodes are formed on the outer surface of the ceramic sintered body to be electrically connected to the coil conductor.
In the laminated inductor, the number of stacked ceramic green sheets is increased to increase the number of turns, and thereby produce high inductance.
However, in the method of printing the internal electrode paste defining a coil conductor on each of the ceramic green sheets, a step between a portion having the internal electrode paste provided therein and a portion without the internal electrode paste in the resultant laminate increases as the number of stacked ceramic green sheets increases. Therefore, in pressing the laminate in the thickness direction before firing, press-bonding distortion occurs. Further, interlaminar peeling referred to as xe2x80x9cdelaminationxe2x80x9d due to the press-bonding distortion after firing also occurs.
Additionally, in the laminated inductance, the thickness or the width of a coil conductor must be increased to decrease DC resistance. However, by the method of forming an internal electrode including the coil conductor by printing the internal electrode paste on the ceramic green sheet, it is difficult to provide an internal electrode having sufficient thickness.
If an internal electrode having sufficient thickness can be provided by repeatedly printing the internal electrode paste several times, the press-bonding distortion significantly increases in pressing the laminate in the thickness direction. Therefore, interlaminar peeling often occurs in the resultant ceramic sintered body.
Furthermore, when the width of the coil conductor is increased to decrease DC resistance, the inductance value is substantially decreased.
The above-described problems occur not only in the laminated inductor but also in other laminated ceramic electronic components. That is, an increase in the number of laminated internal electrodes substantially increases press-bonding distortion when pressing in the thickness direction, thus often causing delamination. Also, an increase in the thickness of the internal electrode to decrease the DC resistance further causes the delamination.
To overcome the above-described problems with the prior art, preferred embodiments of the present invention provide a method of producing a laminated ceramic electronic component which increases the thickness of an internal electrode and decreases DC resistance, and which minimizes delamination even when the number of stacked internal electrodes is increased, and a laminated ceramic electronic component produced according to such a novel method.
Preferred embodiments of the present invention also provide a method of producing a laminated inductor which increases the thickness of a coil inductor as an internal electrode, which causes less delamination even when the number of stacked internal electrodes is increased, and which achieves a greatly increased inductance even when DC resistance is substantially decreased.
In a first preferred embodiment of the present invention, a method of producing a laminated ceramic electronic component includes the steps of printing ceramic paste on a carrier film except in a portion where an internal electrode is to be formed and the vicinity thereof, printing internal electrode paste on the portion where an internal electrode is to be formed to define a green sheet including a ceramic paste layer and an internal electrode paste layer, both of which are provided with a space therebetween, repeatedly press-bonding the laminate including the green sheet and the carrier film to another green sheet and then separating the carrier film such that the green sheets are stacked to obtain a ceramic laminate, and firing the ceramic laminate to obtain a ceramic sintered body. In this step, the other green sheets may or may not be supported by the carrier films.
In the method of producing a laminated ceramic electronic component according to the first preferred embodiment of the present invention, the ceramic paste printing step is performed either after or before the internal electrode paste printing step.
In the method of producing a laminated ceramic electronic component according to the first preferred embodiment of the present invention, the step of press-bonding the green sheet having the internal electrode paste layer provided thereon and supported by the carrier film and then separating the carrier film is repeated for a plurality of the green sheets including the internal electrode paste layers provided therein and having substantially the same shape to define an internal electrode having a thickness corresponding to the total thickness of a plurality of stacked internal electrode paste layers.
In a second preferred embodiment of the present invention, a method of producing a laminated ceramic electronic component includes the steps of providing first and second composite sheets each of which is supported by a carrier film, and each of which includes an internal electrode paste layer and a ceramic green sheet layer, which are provided with a space therebetween such that the internal paste layer passes through the ceramic green sheet from one of two main surfaces to the other of the two main surfaces, press-bonding the first composite sheet to another green sheet on a lamination stage, and then separating the carrier film, laminating the second composite sheet on the first composite sheet, press-bonding both sheets, and then separating the carrier film of the second composite sheet to define an internal electrode including a lamination of the internal electrode paste layers of the first and second composite sheets, and sintering the laminate obtained in the lamination step to obtain a ceramic sintered body.
In a third preferred embodiment of the present invention, a method of producing a laminated ceramic electronic component includes the steps of providing an electrode green sheet which is supported by a carrier film, and which includes an internal electrode for inductance configured to pass through a ceramic layer from the upper surface to the lower surface thereof, and the ceramic layer provided around the internal electrode with a space therebetween, providing a connecting electrode green sheet which is supported by a carrier film, and which includes a connecting electrode exposed from the upper and the lower surfaces of a ceramic layer, and the ceramic layer provided around the connecting electrode with a space therebetween, laminating a plurality of the electrode green sheets and the connecting electrode green sheets while separating the carrier films such that the internal electrodes for inductance are electrically connected through the connecting electrodes to define a coil to obtain a laminate, and firing the laminate to obtain a ceramic sintered body.
In the method of producing a laminated ceramic electronic component according to the third preferred embodiment of the present invention, a plurality of the electrode green sheets including the internal electrodes for inductance having substantially the same shape are laminated to define an internal electrode including a plurality of layers.
In the method of producing a laminated ceramic electronic component according to the third preferred embodiment of the present invention, in the lamination step, the carrier films are separated after press-bonding of the electrode green sheets and the connecting electrode green sheets.
In a fourth preferred embodiment of the present invention, a method of producing a laminated ceramic electronic component includes the steps of forming an electrode green sheet which is supported by a carrier film, and which includes an internal electrode for inductance configured to be exposed from the upper and lower surface of a ceramic layer, and the ceramic layer provided around the internal electrode with a space therebetween, forming a plurality of the electrode green sheets while separating the carrier films such that the internal electrodes are electrically connected to each other to define a coil conductor to obtain a laminate, and firing the laminate to obtain a ceramic sintered body.
In the method of producing a laminated ceramic electronic component in the fourth preferred embodiment of the present invention, the carrier films are separated after press-bonding of the electrode green sheets.
In the method of producing a laminated ceramic electronic component in the fourth preferred embodiment of the present invention, a plurality of the electrode green sheets including the internal electrodes for inductance having substantially the same shape are laminated to define an internal electrode including a plurality of layers.
In the method of producing a laminated ceramic electronic component in each of the first to fourth preferred embodiments of the present invention, the space may be filled with a void forming material which is burned away in subsequent firing. As the void forming material, carbon paste or a synthetic resin is used.
In a fifth preferred embodiment of the present invention, a method of producing a laminated ceramic electronic component includes the step of preparing a composite green sheet which is supported on a carrier film, and which includes an internal electrode paste layer provided to extend through a ceramic green sheet from one of two main surfaces to the other of the two main surfaces and the ceramic green sheet layer provided around the internal electrode paste layer with a space therebetween, providing a void forming green sheet which is supported on a carrier film and which includes a void forming material layer burned down in firing and configured to pass through a ceramic green sheet layer from one of two main surfaces to the other thereof and to overlap the internal electrode paste layer of the composite sheet when laminated thereon, and the ceramic green sheet provided around the void forming material layer, press-bonding the composite green sheet to another green sheet on a lamination stage and then separating the carrier film, the step of laminating the void forming green sheet on the composite green sheet, press-bonding both green sheets and then separating the carrier film to laminate the void forming material layer on the internal electrode paste layer, and repeating the lamination step, laminating unpatterned ceramic green sheets on the upper and lower surfaces of the resultant laminate, and then firing the laminate to burn down the void forming materials layers to obtain a ceramic sintered body in which a void is provided in at least one of the upper and lower surfaces of an internal electrode.
In a sixth preferred embodiment of the present invention, a method of producing a laminated ceramic electronic component includes the steps of providing a composite green sheet which is supported on a carrier film, and which includes an internal electrode for inductance configured to pass through a ceramic green sheet from the upper surface to the lower surface thereof, and the ceramic green sheet layer provided around the internal electrode for inductance with a space therebetween, providing a connecting electrode green sheet which is supported on a carrier film and which includes a void forming material layer composed of a material burned down in firing and configured to overlap the internal electrode for inductance of the composite sheet when laminated thereon and pass through the connecting electrode green sheet from the upper surface to the lower surface thereof, a connecting electrode provided at one end of the void forming material layer to be exposed from the upper and lower surfaces, and a ceramic green sheet layer provided around the void forming material layer and the connecting electrode, laminating a plurality of the composite green sheets and the connecting electrode green sheets such that the internal electrodes for inductance are electrically connected through the connecting electrodes, and the void forming material layer overlaps at least one of the upper and lower surfaces of each of the internal electrodes for inductance, and further laminating unpatterned green sheets on the upper and lower surfaces on the laminate, and firing the laminate to obtain a ceramic sintered body in which a void is provided in contact with at least one of the upper and lower surfaces of the internal electrodes for inductance,
In the fifth and sixth preferred embodiments of the present invention, as the void forming material, carbon paste or a synthetic resin is preferably used.
In a seventh preferred embodiment of the present invention, a laminated ceramic electronic component includes a ceramic sintered body formed by integrally firing a plurality of ceramic layers together with an internal electrode, and the internal electrode provided in the ceramic sintered body, wherein the internal electrode has a thickness corresponding to the total thickness of the plurality of ceramic layers.
In the seventh preferred embodiment of the present invention, a gap is provided outside at least one of the upper and lower surfaces of the internal electrode.
In the laminated ceramic electronic component according to the seventh preferred embodiment of the present invention, a plurality of the internal electrodes are electrically connected in the ceramic sintered body.
In the laminated ceramic electronic component according to the seventh preferred embodiment of the present invention, the plurality of the internal electrodes are electrically connected through connecting internal electrodes.
Other features, elements, characteristics and advantages of the present invention will become more apparent from the detailed description of preferred embodiments thereof with reference to the drawings.